Build Up Of Mineral Deposits On The Tiles

by Lynn

Build Up Of Mineral Deposits On The Tiles In The Pool At The Water Line

by Lynn
(Tucson, AZ)

Our small community pool (serves an HOA of 50 homes) has been plagued this year with a build up of mineral deposits along the water line on the tiles inside the pool. We were recently cited by the health inspector for the problem (saying it could be a source for the growth of algae) -

With hard work using a pumice stone and a scouring pad we removed the stuff, but it is now coming back quickly and seems to be getting worse. Our pool company service man attributes the build up to hard water and is recommending adding a solution (what I'm not sure) regularly to keep the minerals from forming -

That's the story. The question is - how do we prevent buildup on the tiles (is it a chemical problem, a hard water problem or something else) and what is the easiest way to control it?

Thanks for the question Lynn. I know about hard water levels in Arizona. For years I had a pool route in the Mesa/Tempe area. Arizona is definitely one of the states with hard water. A pumice stone and scouring pads are good but that's only a quick fix.

Without the calcium hardness reading it's difficult to say whether it's the water hardness or something else. That something else could be water leaking out of the grout. This can also cause a ring around the pool and is attributed to hardness
of water scale. The only way I know to combat this issue is to remove the tile then seal it with a water proofer such as Thoroseal.

Here are some things you can to do lessen the effects of water hardness:

Never use calcium hypochlorite. This is a granular chlorine and the name says it all. You're adding more calcium (hardness) to the pool.

Keep the TA (total alkalinity) between 80 - 100ppm

Lower your pH to 7.0 - 7.2. This will cause the pool to become a little more acidic and soften any calcium rings that may pop up.

Absolutely no calcium chloride

The pool guy might be talking about a product called Lo-Chlor Calcium Hardness Reducer. It's Hydroxyethylidene Diphosphonic Acid Complex and can be found at Sears, Amazon, and Walmart. Another one is called Metal Out. This is normally not a one shot deal. A metal sequestrant does not remove metal and/or hardness from the pool water, per se. It holds it in solution until it can get filtered. Then you backwash the metal out.

Because metal sequestrants break down over time and get filtered and backwashed out, you will need to add a bottle once per week. If the above doesn't work the only thing to do is to drain and refill. I've had to do this many times on my route because Arizona water is simply so irritatingly hard. You also can have the water trucked in. It's normally about 1 - 2 cents per gallon.

Hope this helps and have a great Summer.


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